tclmain is a single Tcl file which supports running of Tcl applications directly from the package directory without the need to install them in a folder belonging to the users PATH variable.
Wikipage for discussion: https://wiki.tcl-lang.org/page/tclmain
The program tclmain provides the same feature as Python with its syntax `python -m modulename` does. tclmain looks in the package folder for files ending with `_main.tcl` or `_doc.tcl` etc. You can execute this files then with the following syntax:
tclmain -m pkgname main
Instead of -m as well -p is supported.
If the package does not provide these files the user can place such files as well in its config folder ~/.config/tclmain` on a Unix system.
The advantage in comparison is that there is a unified interface for running tcl application for the user. The developer does not need anymore an installation of the applications in the users PATH, just installing the package is enough.
For more information and examples look at the homepage and at the Wiki page.